Expansion
Ghrelin stimulates hunger; leptin, PYY and GLP-1 promote satiety
Expansion
Orexigenic (hunger)
- Ghrelin, from the gastric fundus. Rises before meals and falls after eating. The only significant appetite-stimulating gut hormone
Anorexigenic (satiety)
- Leptin, from adipose tissue: a long-term signal of energy stores
- Peptide YY, from L cells of the ileum and colon
- GLP-1, from L cells: also an incretin, slowing gastric emptying
- Cholecystokinin: short-term meal termination
- Insulin and amylin
All converge on the hypothalamic arcuate nucleus, which contains appetite-stimulating NPY/AgRP neurones and appetite-suppressing POMC/CART neurones, projecting to the paraventricular and lateral hypothalamic nuclei.
Two clinical illustrations: congenital leptin deficiency causes severe early obesity and responds dramatically to leptin, whereas common obesity involves leptin resistance, so leptin levels are high and treatment ineffective. And bariatric surgery works partly by reducing ghrelin and greatly increasing GLP-1 and peptide YY, which is why it changes appetite rather than simply restricting volume.